This project will apply quantitative analyses of behavioral choice to situations that involve social reinforcers, defined here as positively reinforcing events that are mediated by the actions of another person (e.g., attention, approval, affection); and social contexts, defined here as those marked by stimuli that are reliable cues for the availability of social reinforcers (e.g., the immediate presence of a familiar person). The goals of the project are to develop methods for maximizing adaptive sensitivity to social reinforcement contingencies and minimize maladaptive behavioral allocations in social contexts. One set of basic studies will examine sensitivity to reinforcement contingencies in social and nonsocial contexts. Sensitivity refers to the degree to which the individual's behavioral allocation among concurrently available alternatives matches the relative amounts of reinforcement that are obtained from those alternatives. If sensitivity is high, reinforcement is maximized as behavior is re-allocated in response to changes in reinforcement contingencies. The basic studies will be conducted in automated testing environments where experimental sessions in which the presence/absence of an adult in the immediate environment will be rigorously controlled as experimental variable. These studies will develop methods for determining individual profiles of contingency sensitivity in social vs. nonsocial contexts. Our hypothesis is that adaptive behavior is maximized when sensitivity is unaffected by context shifts. We will test this hypothesis by examining the acquisition of new behavior in social vs. nonsocial contexts with individuals who have a range of social-reinforcer profiles. We will also investigate procedures for improving maladaptive profiles in both social and nonsocial contexts, and the subsequent effects of improvements on learning. A second set of studies will examine social reinforcer function in relation to the well-documented deficit in the development of joint attention in young children with autism and related disorders (PDD-NOS). Joint attention refers to the use of gestures, verbalizations, and gaze shifts to coordinate attention with another person in order to share the experience of an object or event. The proposed research will examine correlations between quantitative measures of preference and sensitivity for social reinforcers and the results of assessments of joint attention initiation and develop training procedures that target specific behavioral prerequisites for joint attention initiation. These prerequisites are derived from a functional analysis of joint attention initiation. We will monitor concurrent changes in preference, contingency sensitivity, and joint-attention initiation as training progresses.